等差数列an的前n项和是Sn,且a4+a8=0,则A.S4

等差数列an的前n项和是Sn,且a4+a8=0,则A.S4 等差数列｛an｝3a4=7a7,且a1>0sn是等差数列｛an｝的前n项和,若sn取最大值, 设数列an是等差数列,且a4=负4,a9=4,Sn是数列an的前n项和则 A.S5 Sn是等比数列an的前n项和,S4,S2,S3成等差数列,且a2+a3+a4= 设Sn是等差数列｛an｝的前n项和,已知3a4=7a7,且a1＞0,当Sn取最大值时,求n! 已知数列｛an}是公差不为零的等差数列且a1=1,且a2,a4,a8成等比数列.①求通项an②若bn=1/[an*a(n+1)],求｛bn｝的前n项和Sn {an]是等差数列,sn是是{an]前n项的和,且a1,a3,a4是等比数列,则（S3-S2）/（S5-S3）等于如题 设Sn是等差数列an的前n相和,且a1=1,a4=7.S5? 已知{an}是等差数列,且{sn}是{an}的前n项和,a1,a3,a4成等比数列,求(s3-s2)/(s5-s3)的值快 已知{an}是等差数列,且{sn}是{an}的前n项和,a1,a3,a4成等比数列,求(s3-s2)/(s5-s3）的值 等差数列{An}的前n项和为Sn,且满足A3*A4=117,A2+A5=22 求通项An ；若数列{Bn}是等差数列,且Bn=Sn/(n+c),求 等差数列an前n项和为Sn,且6Sn-5S3=5,a4=错了，是6S5-5S3=5，求a4 已知等差数列an的前n项和为Sn,且满足a2+a4=14,S7=70 已知Sn为等差数列{an}的前n项和,且a4=2a3,则S7/S5=? 等差数列{an}的前n项和为Sn,且6S5-5S3=5,则a4= 等差数列{an}的前n项和为Sn,且6S5-5S3=5,则a4= 等差数列{an}的前n项和为Sn,且6S5-5S3=5,则a4=______. 已知等差数列an的前n项和为Sn,且a4为10,S4为22,求通项公式,